Anisotropic conductive sheet

ABSTRACT

An anisotropic conductive sheet for high frequencies is provided as elastomer for connecting high-integrated circuit boards and fine pitch electronic components of recent years. Anisotropic conductive sheet ( 30 ) has a sheet-shaped elastomer ( 1   c ), and a non-conductive rectangular first penetrating region ( 11 ) is formed vertically and horizontally in a state surrounded by the sheet-shaped elastomer ( 1   c ). In addition, an electrically-conductive second penetrating region ( 12 ) is formed in a rectangular manner in a state surrounded by the first penetrating region ( 11 ). The first penetrating region  11  can be a high-dielectric rectangular third penetrating region. The anisotropic conductive sheet ( 30 ) has an effect in that electrostatic shield is provided between connected electronic components.

FIELD OF THE INVENTION

The present invention relates to an anisotropic conductive sheetdisposed between circuit boards such as printed circuit boards andvarious circuit components.

RELATED ART

In recent years, more and more electronic devices have reduced theirsizes and widths and it has become dramatically desirable to implement aconnection between small circuits or a connection between a smallcomponent and a small circuit. As examples of such connections, theremay be solder joining or joining with anisotropic conductive adhesives.In another example, an anisotropic conductive elastomer sheet may bedisposed between an electronic component and a circuit board forconduction of electricity therebetween.

An anisotropic conductive elastomer sheet may be referred to as anelastomer sheet that has conductivity in a certain direction only. Someanisotropic conductive elastomer sheets exhibit conductivity only in adirection of width, and others in the direction of width only whenpressed in the direction of width.

If the anisotropic conductive elastomer sheet is employed, it ispossible to implement a compact electronic connection without othermeans such as soldering, mechanical fitting and so on, and also possibleto absorb mechanical impact and strain. Therefore, anisotropicconductive elastomer sheets are widely utilized in many applicationfields such as liquid crystal display, cellular phone, electroniccomputer, electronic digital clock, electronic camera, computer and thelike.

The anisotropic conductive elastomer sheets are also widely used aselectronic connectors for connecting a circuit apparatus such as aprinted circuit board, and a leaderless chip carrier or a liquid crystalpanel. An elastomer connector is a connector utilizing elastomer such asconductive rubber disposed between electrodes to obtain an electricalconnection simply by pressing the electrodes. One of such types ofelastomer connectors may include an anisotropic conductive elastomersheet having properties of being insulative in a horizontal directionand conductive in a vertical direction.

In the testing of electrical connections of circuit apparatus such asprinted circuit boards and semiconductor integrated circuits, a sheet ofanisotropic conductive elastomer is interposed and makes an electricalconnection between an electrode region to be tested which is formed onat least one surface of the circuit apparatus to be tested and anelectrode region of the testing circuit board which is formed on atleast one surface of the testing circuit board.

Conventionally, it is known that an anisotropic conductive block isfirstly formed by integrating aligned metal wires by using insulator andthe resultant block is then sliced in a direction perpendicular to thedirection of the metal wire so as to make an anisotropic conductiveelastomer sheet. (As an example, referring to Japanese Laid-Open PatentPublication No. 2000-340037)

The use of metal wire in the anisotropic conductive elastomer sheet,however, makes it difficult to shorten the distance between the wires,therefore it is not easy to surely obtain the fine pitch that isdemanded for anisotropic conductivity in the highly integrated circuitboards and electrical components in recent years. Metal wires aresusceptible to a compressive buckling and may be dropped off from thesheet when used repeatedly such that the anisotropic sheet may not fullyconduct performance thereof.

Although inductance and capacitance due to wiring patterns are minimal,these could become more serious for high-frequency applications andcause noise generation. When high-frequency electric current flowsthrough the wiring patterns, emission of electro-magnetic waves and skineffect may arise and the noise generation may be caused. In particular,the clock frequency may reach 10 GHz with some devices such as hybrid ICand micro-wave IC.

In order to avoid such situations, twisted pair wire or a coaxial cablewhich can be shielded electromagnetically by appropriately grounding thecable shield with external conductor is employed in order to minimizemutual inductance with the electrical wire. In a pattern wiring on aprinted board, strip lines may be formed to keep the impedance constant.

However, in elastomer connectors, the above described may not be appliedsuch that it is desirable to obtain an elastomer connector which hardlycauses noise generation and the like in high-frequency applications.

SUMMARY OF THE INVENTION

From the above, it is an object of the present invention to provide ananisotropic conductive sheet for high-frequency applications such as anelastomer connector for connecting a recent integrated circuit board anda fine-pitch electronic component. More specifically, it is an object ofthe present invention to provide an anisotropic conductive sheet beingcharacterized by fine-pitch anisotropic conductivity and electromagneticwave shielding property, wherein such anisotropic properties aremaintained even after repeated use.

It is advantageous that noise from junctions between electroniccomponents can be prevented by connecting electronic components such asprinted boards, cables and devices which transmit high-frequency signalsas well as by ensuring the shield electromagnetic waves property in theelastomer connector. It is also possible to obtain high-admittance ifdielectric material provided between signal lines.

It is also possible to improve the measurement performance by ensuringthe shield electro-magnetic waves property in the elastomer connector inthe electrical examination on the circuit devices such as printedcircuit boards and semiconductor integrated circuits.

More specifically, the following is provided according to the presentinvention.

(1) An anisotropic conductive sheet being electrically conductive inonly one direction, comprising: electrically-conductive sheet-shapedelastomer; at least one non-conductive first penetrating region beingformed as being surrounded by the sheet-shaped elastomer; and anelectrically-conductive second penetrating region being formed as beingsurrounded by the non-conductive first penetrating region.

(2) The anisotropic conductive sheet according to (1), wherein thesecond penetrating region is interspersed in the sheet-shaped elastomer.

(3) The anisotropic conductive sheet according to (1) or (2), whereinthe second penetrating region is aligned with regularity in thesheet-shaped elastomer.

(4) The anisotropic conductive sheet according to any one of (1) to (3),wherein the second penetrating region has higher conductivity than thesheet-shaped elastomer.

(5) The anisotropic conductive sheet according to any one of (1) to (4),wherein the first penetrating region and the second penetrating regionare formed in a concentric manner.

(6) The anisotropic conductive sheet according to any one of (1) to (4),wherein the first penetrating region and the second penetrating regionare formed in a rectangular manner, and the rectangular firstpenetrating region and the rectangular second penetrating region arepositioned with a same center of gravity.

(7) An anisotropic conductive sheet being electrically conductive inonly one direction, wherein: the anisotropic conductive sheet has anelectrically-conductive sheet-shaped elastomer; at least onehigh-dielectric third penetrating region is formed as being surroundedby the sheet-shaped elastomer; and an electrically-conductive secondpenetrating region is formed as being surrounded by the thirdpenetrating region.

(8) The anisotropic conductive sheet according to claim 7, wherein thesecond penetrating region is interspersed in the sheet-shaped elastomer.

(9) The anisotropic conductive sheet according to (7) or (8), whereinthe second penetrating region is aligned with regularity in thesheet-shaped elastomer.

(10) The anisotropic conductive sheet according to any one of (7) to(9), wherein the second penetrating region has higher conductivity thanthe sheet-shaped elastomer.

(11) The anisotropic conductive sheet according to any one of (7) to(10), wherein the third penetrating region and the second penetratingregion are formed in a concentric manner.

(12) The anisotropic conductive sheet according to any one of (7) to(10), wherein the third penetrating region and the second penetratingregion are formed in a rectangular manner, and the rectangular thirdpenetrating region and the rectangular second penetrating region areplaced with a same center of gravity.

(13) The anisotropic conductive sheet according to any one of (7) to(12), wherein the third penetrating region comprises ferroelectricsubstance.

(14) A pair of electronic components which are connected with theanisotropic conductive sheet according to any one of (1) to (13).

According to the present invention, there is provided an anisotropicconductive sheet which is electrically conductive in only one direction,wherein at least one non-conductive first penetrating region is formedwithin the sheet-shaped elastomer which is electrically conductive inonly one direction such as to be surrounded thereby, and the secondpenetrating region which is electrically conductive in only onedirection is formed within the non-conductive first penetrating regionsuch as to be surrounded thereby.

The term “anisotropic conductive sheet” may be a flexible anisotropicconductive sheet which has a predetermined thickness, as well as apredetermined front surface and a predetermined back surface in frontand back, or on up and down of the thickness. It may be an ordinaryfeature to have “a predetermined thickness, as well as a predeterminedfront surface and a predetermined back surface in front and behind, oron up and down of this thickness.” In other words, this anisotropicconductive sheet has a certain thickness and has a front surface and aback surface in the direction perpendicular to the thickness direction.That the sheet is “flexible” may mean that the sheet can be bentelastically.

“Electrically-conductive sheet-shaped elastomer” can be considered to bea sheet-shaped elastomer having electrical conductivity and can besufficiently high conductivity. It also can be sufficiently lowelectrical resistance. The sheet-shaped elastomer is the main body ofthe anisotropic conductive sheet according to the present invention andhas at least one hole piercing the sheet in the section wherein thepenetrating regions, described hereafter, are formed. Non-conductivefirst penetrating region or third penetrating region is formed in thishole section. Therefore, the conduction direction of the anisotropicconductive sheet, as a whole, is only a certain direction (namely, ifthe drawing direction of the anisotropic conductive sheet is horizontal,vertical direction perpendicular thereto). The anisotropic conductivesheet according to the present invention, having anelectrically-conductive sheet-shaped elastomer, has sufficientconductivity in the conduction direction.

Being non-conductive may mean that conductivity is sufficiently low andmay mean that electrical resistance is sufficiently high. Becausenon-conductive first or third penetrating region is formed within theelectrically-conductive sheet-shaped elastomer in the anisotropicconductive sheet of the present invention, the anisotropic conductivesheet, as a whole, comprises non-conduction direction which is notconductive. Because the anisotropic conductive sheet according to thepresent invention has a non-conductive penetrating region which issurrounded by the sheet-shaped elastomer, it has sufficientnon-conductivity in the non-conduction direction of the anisotropicconductive sheet.

“Electrically-conductive elastomer” is referred to as elastomer which iselectrically conductive and can generally be elastomer to whichelectrically-conductive material is combined to lower volume resistivity(for example, 1 Ωcm or below). More particularly, it can be elastomerwhich is obtained by combining electrically-conductive material tonon-conductive elastomer material. Natural rubber, polyisoprene rubber,butadiene copolymers such as butadiene-styrene, butadiene-acrylonitrile,and butadiene-isobutylene, conjugated diene rubber, and hydrogenadditives thereof are used as non-conductive elastomer materials. Inaddition, block copolymer such as styrene-butadiene-diene blockcopolymer rubber and styrene-isoprene block copolymer, the hydrogenadditives thereof, chloroprene polymer, vinyl chloride-vinyl acetatecopolymer, polyurethane rubber, polyester rubber, epichlorohydrinrubber, ethylene-propylene copolymer rubber, ethylene-propylene-dienecopolymer rubber, soft liquid-form epoxy rubber, silicone rubber,fluorocarbon rubber or the like are also used as non-conductiveelastomer materials.

Out of these, silicone rubber, which is superior in heat-resistance,cold-resistance, chemical-resistance, weather-resistance, electricalinsulation and safety property, is preferably used.Electrically-conductive elastomer can be obtained by combiningelectrically-conductive materials such as pure metal, metal alloy,non-metallic powder (flakes, chips, foil, etc, as well) to suchnon-conductive elastomer material. Gold, silver, copper, nickel,tungsten, platinum, palladium and the like are given as examples of thepure metals. As the other metals, stainless steel (SUS), phosphorbronze, beryllium copper and the like are given. The non-metallic powdermay include carbon and the like, and the carbon powder may includecarbon nanotube, fullerene, etc.

“Electrically-conductive second penetrating region” can indicate oneconductive thin-layer (called “metal layer” if composed of metal) formedwithin the non-conductive first penetrating region or high-dielectricthird penetrating region such as to occupy a given area. If this is ametal layer, this can include instances wherein the entire metal layeris composed of one type of metal. In addition, the second penetratingregion can have a function for electrically connecting the front surfaceside and the back surface side of the anisotropic conductive sheet.

The penetrating region can be considered to be formed such that thefront surface and back surface of the anisotropic conductive sheet havea predetermined area, have thickness (namely, penetrates from the frontsurface of the anisotropic conductive sheet to the back surface), andhave volume as materiality. In addition, the same of the penetratingregion can be any shape in the front surface or the back surface of thesheet-shaped elastomer (or in the vicinity thereof). The shape of thepenetrating region expressed on the front surface or back surface of thesheet-shaped elastomer can, for example, be circular or rectangular.

“Sheet-shaped” refers to a commonly conceived sheet-shaped flat plateand can be a circular plate or a rectangular plate. However, it ispreferable that the plate thickness of the sheet-shaped elastomer isthin and as even as possible.

As non-conductive elastomer which is not electrically conductive isreferred to and elastomer not including electrically-conductivematerials may be referred to.

That a “first penetrating region is formed within the sheet-shapedelastomer such that the region is surrounded by the elastomer” can meanthat the outer edge of the first penetrating region is surrounded by thesheet-shaped elastomer. Similarly, that a “second penetrating region isformed within the first penetrating region such that the secondpenetrating region is surrounded by the first penetrating region” canmean that the outer edge of the second penetrating region is surroundedby the first penetrating region, and the outer edge of the secondpenetrating region is not in direct contact with the sheet-shapedelastomer. Furthermore, the analogy can be applied by replacing thefirst penetrating region with the third penetrating region.

In the present invention, high-dielectric third penetrating region isformed in at least one location in the electrically-conductivesheet-shaped elastomer, and the electrically-conductive secondpenetrating region is formed in the high-dielectric third penetratingregion.

The “dielectric”, stated herein, can be referred to as the relativepermittivity. This permittivity differs according to the property of thethird penetrating region. The high-dielectric third penetrating regioncan be considered to have a higher permittivity than the permittivity ofthe non-conductive first penetrating region.

The high-dielectric third penetrating region, therefore, can be composedof material having high permittivity. The material having highpermittivity may, for example, include Ferroelectric substance.

Perovskite oxides such as barium titanate (BaTiO₃), lead titanate(PbTiO₃), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃) and thelike are given as examples of “ferroelectric substances”. The thirdpenetrating region can include chips, particles, flakes or powdersformed from these materials.

Further, in the present invention, the electrically-conductive secondpenetrating region is interspersed in the electrically-conductivesheet-shaped elastomer while being surrounded by the first or thirdpenetrating region.

That “the second penetrating region is interspersed” does notnecessarily mean that the second penetrating region is interspersedrandomly. In other words, the second penetrating region can be placed inthe sheet-shaped elastomer either regularly or randomly. If there are aplurality of second penetrating regions, these second penetratingregions are dispersed in the sheet-shaped elastomer and alignedappropriately. Further, in correspondence to the placement of the secondpenetrating regions, the first or third penetrating region is alsodispersed in the sheet-shaped elastomer and aligned appropriately. Inother words, if a plurality of penetrating regions of the same type areprovided in the same sheet-shaped elastomer in a plurality of locations,respectively, the adjacent penetrating regions of the same type do notshare regions with each other (first penetrating regions with eachother, second penetrating regions with each other, or third penetratingregions with each other).

Furthermore, in the present invention, the electrically-conductivesecond penetrating region is aligned with regularity in theelectrically-conductive sheet-shaped elastomer.

Although to be “aligned with regularity” shows an appropriate placementpattern, more specifically, it may be considered to align the circularor rectangular second penetrating regions in a grid pattern in theanisotropic conductive sheet. The grid-shape in this case can berectangular or rhombic. Further, the circular or rectangular secondpenetrating regions can be aligned, evenly spaced, in one row.Furthermore, preferably, the second penetrating region can be aligned ina matrix.

With regards to the alignment pitch of the second penetrating region,1/10 inch- or, in other words, 2.54 mm-interval alignment can beconsidered if adjusting it to the land pattern placement of the printedboard.

Further, the alignment pitch of the second penetrating region is, forexample, preferably approximately 70 micrometers or smaller if adjustingit to fine pitch wherein the alignment pitch of the pad on the IC chip,the inner lead, or the outer lead is constricted.

Furthermore, in the present invention, the electrically-conductivesecond penetrating region has higher conductivity than theelectrically-conductive sheet-shaped elastomer.

Here, the resistance between ordinarily connected ports of theelectrically-conductive elastomer can be 100 to 1000Ω, and theresistance between ordinarily connected ports of theelectrically-conductive second penetrating region is preferably 30Ω orlower. The electrically-conductive elastomer can include elastomer whichis electrically conductive per se, elastomer which becomes electricallyconductive by pressure-welding, and anisotropic conductive elastomerwhich is electrically conductive in only one direction.Electrically-conductive sheet-shaped elastomer can be, for example,elastomer obtained by combining electrically-conductive materials suchas graphite with non-conductive elastomer material and forming intosheet-shaped. The electrically-conductive second penetrating region can,for example, be elastomer obtained from combining qualityelectrically-conductive materials such as gold and silver tonon-conductive elastomer material and can be one conductive thin-layer(a metal layer if composed of metal).

Then, the selection of these conductive materials or the volumeresistivity value of the electrically-conductive second penetratingregion according to the combination ratio of the conductive materials tothe non-conductive elastomer material can be set accordingly.

Furthermore, in the present invention, the non-conductive firstpenetrating region and the electrically-conductive second penetratingregions are formed in a concentric manner.

The electrically-conductive second penetrating region, theelectrically-conductive sheet-shaped elastomer, and the non-conductivefirst penetrating elastomer of such anisotropic conductive sheetrespectively correspond to the internal conductor composed of strandedwire (core wire), the outer conductor composed of braiding formed fromthin conductive wire, and non-conductor as a spacer between the internalconductor and the outer conductor, and attempts to ensure theelectromagnetic wave shielding property in the elastomer connector inthe junctions between electronic parts.

In addition, the non-conductive first penetrating region is formed in arectangular manner, the electrically-conductive second penetratingregion is formed in a rectangular manner, the rectangular firstpenetrating region and the rectangular second penetrating region ispositioned with the same center of gravity, and the present inventionattempts to ensure the electro-magnetic wave shielding property in theelastomer connector in the junctions between electronic parts, as in theforegoing.

These non-conductive first penetrating region andelectrically-conductive second penetrating region can be formed as anintegrated component. The coupling agent for coupling these conductiveelastomers and non-conductive elastomers is a bonding agent for couplingthese components and can include common commercially-available adhesiveagent. More specifically, it can be a coupling agent such as silane,aluminum, and titanate, and silane coupling agent is preferably used.

Furthermore, in the present invention, the high-dielectric thirdpenetrating region and the electrically-conductive second penetratingregion are formed in a concentric manner.

The electrically-conductive second penetrating region, theelectrically-conductive sheet-shaped elastomer, and the high-dielectricthird penetrating elastomer of such anisotropic conductive sheetrespectively correspond to the internal conductor composed of strandedwire (core wire), the outer conductor composed of braiding formed fromthin conductive wire, and dielectric material as a spacer between theinternal conductor and the outer conductor, and is such that makes theelastomer connector in the junctions between electronic partshigh-admittance and ensures the ability thereof to shieldelectro-magnetic waves.

In addition, the high-dielectric third penetrating region is formed in arectangular manner, the electrically-conductive second penetratingregion is formed in a rectangular manner, the rectangular thirdpenetrating region and the rectangular second penetrating region ispositioned with the same center of gravity, and the present inventionmakes the elastomer connector in the junctions between electronic partshigh-admittance and ensures the ability thereof to shieldelectro-magnetic waves.

As an application example of the present invention, the anisotropicconductive sheet is connected to a pair of electronic components. A pairof electronic components is one pair of electronic components and refersto a component for sandwiching the anisotropic conductive sheet betweenthis pair of electronic components. A printed board or an electricalcomponent of fine pitch (for example, a semiconductor integratedcircuit) are examples of such electronic components. The pairedelectronic components can be the same type of electronic component orcan be a pair of differing electronic components such as a printed boardand a semiconductor integrated circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an anisotropic conductive sheetaccording to a first embodiment of the present invention.

FIG. 1B is a perspective view of an anisotropic conductive sheetaccording to a second embodiment of the present invention,

FIG. 2A is a perspective view of an anisotropic conductive sheetaccording the present invention wherein a plurality of rectangularpenetrating regions is formed.

FIG. 2B is a perspective view of an anisotropic conductive sheetaccording the present invention wherein a plurality of circularpenetrating regions is formed;

FIG. 3 is a perspective view for showing the manufacturing process ofthe anisotropic conductive sheet in FIG. 2A.

FIG. 4A is a perspective view for showing the manufacturing processsubsequent to FIG. 3.

FIG. 4B is a perspective view for showing the manufacturing processsubsequent to FIG. 4A.

FIG. 5 is a perspective view for showing the manufacturing method of theanisotropic conductive sheet in FIG. 2B.

FIG. 6A is a perspective view for showing the manufacturing processsubsequent to FIG. 5.

FIG. 6B is a perspective view for showing the manufacturing processsubsequent to FIG. 6A,

FIG. 7 is a perspective view showing an anisotropic conductive sheetaccording to an embodiment wherein a metallic metal layer is used as thesecond penetrating region of the present invention.

FIG. 8 is a partially enlarged view enlarging the upper left corner ofthe anisotropic conductive sheet in FIG. 7.

FIG. 9 is a diagram for showing the manufacturing process of theanisotropic conductive sheet in FIG. 7.

FIG. 10 shows an aspect wherein a laminated body is formed by layering aplate composed of non-conductive material attached with metal and anon-conductive bridge-shaped component, with regards to themanufacturing process of the anisotropic conductive sheet in FIG. 7.

FIG. 11 is a diagram wherein a laminated body is formed by furtherlayering a plate composed of electrically-conductive material on thelaminated body in FIG. 10.

FIG. 12 shows a state wherein a plurality of laminated bodies formed inthe process in FIG. 11 is aligned.

FIG. 13 shows an aspect wherein a block is formed by further sandwichinga conductive sheet component between the laminated bodies in FIG. 12 anda process for cutting the laminated bodies.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the embodiments of the present invention are describedhereafter, with reference to the drawings, the present invention is notlimited to the present embodiments since the present embodiments showconcrete materials and numerical values as preferred examples.Hereafter, like elements are designated to like numerical references andexplanations thereof are omitted or simplified.

FIG. 1A is an appearance diagram of a rectangular anisotropic conductivesheet according to a first embodiment of the present invention, and FIG.1B is that of a circular anisotropic conductive sheet according to asecond embodiment of the present invention. Anisotropic conductivesheets 10 and 20 are sheet-shaped and respectively compriseelectrically-conductive sheet-shaped elastomer 1 a and 1 b. Anon-conductive first penetrating region 11 is formed in the anisotropicconductive sheet 10 such as to be surrounded by the sheet-shapedelastomer 1 a. Similarly, a non-conductive first penetrating region 21is formed in the anisotropic conductive sheet 20 such as to besurrounded by the sheet-shaped elastomer 1 b.

Furthermore, an electrically-conductive second penetrating region 12 isformed in the anisotropic conductive sheet 10 being surrounded by thefirst penetrating region 11, and an electrically-conductive secondpenetrating region 22 is formed in the anisotropic conductive sheet 20being surrounded by the first penetrating region 21, as well.

The sheet-shaped elastomer 1 a, first penetrating region 11, and secondpenetrating region 12, which constitutes the anisotropic conductivesheet 10, are all formed in a rectangular manner. On the other hand, thesheet-shaped elastomer 1 b, first penetrating region 21, and secondpenetrating region 22, which constitutes the anisotropic conductivesheet 20 in FIG. 1B, are all formed in a circular shape. Thesheet-shaped elastomer 1 a, first penetrating region 11, and secondpenetrating region 12 are positioned such that the center points overlapor, in other words, with the same center of gravity, and thesheet-shaped elastomer 1 b, first penetrating region 21, and secondpenetrating region 22 are positioned in a concentric manner.

Although an example that the first and second penetrating regions arecircular or rectangular is shown in the first and second embodiments,the shape of the first and second penetrating regions can be differentas desired. It can, for example, be a polygon, an ellipse, and othershapes such as a closed curved surface.

In the first and second embodiments, the non-conductive firstpenetrating region 11 and 21 can be replaced with a high-dielectricthird penetrating region. In this case, the third penetrating region maybe formed from dielectric sheet wherein sheet-shaped elastomer comprisesparticles of high-dielectric ferroelectric substance. In particular, itcan be formed by using material wherein barium titanate (BaTlO₃) ismixed with silicone rubber. The third penetrating region has the sameshape as the first penetrating region 11 and 21, and is not illustrated.

In the first and second embodiments, the sheet-shaped elastomer 1 a and1 b are formed from components wherein electrically-conductive particlesare combined with silicone rubber. In particular, material wherein fineparticles of carbon allotrope such as graphite are mixed with siliconerubber is used as conductive particles. The first penetrating region 11and 21 are formed from non-conductive material being composed ofsilicone rubber. In addition, the second penetrating region 12 and 22are electrically-conductive material wherein fine particles of silver(Ag) are mixed with silicone rubber as conductive metallic particles.

One example of manufacturing methods of the foregoing anisotropicconductive sheet 10 and 20 is as follows. Mold cavity corresponding tothe shape of the first penetrating region 11 or 21 is punched out fromthe sheet-shaped elastomer 1 a or 1 b, and the first penetrating region11 or 21, formed from non-conductive component, is fitted into this moldcavity. Then, the first penetrating region 11 or 21, as moldingcomponent, is coupled respectively with the sheet-shaped elastomer 1 aor 1 b with coupling agent.

Mold cavity corresponding to the shape of the second penetrating region12 or 22 is punched out from the first penetrating region 11 or 21,beforehand, and the second penetrating region 12 or 22, formed fromconductive component, is fitted into this mold cavity. Then, the secondpenetrating region 12 or 22, as molding component, is coupledrespectively with the first penetrating region 11 or 21 with couplingagent.

Here, the sheet-shaped elastomer 1 a, the first penetrating region 11and the second penetrating region 12 have the same thickness. Similarly,the sheet-shaped elastomer 1 b, the first penetrating region 21 and thesecond penetrating region 22 have the same thickness. By way of example,the thickness t in the drawing is about 0.5 to 1 mm.

Mitsubishi Plastics, Inc. product silicone rubber, Shin-Etsu PolymerCo., Ltd. product silicone rubber and the like are used as elastomer,and Shin-Etsu Polymer Co., Ltd. product silane coupling agent is used asa coupling agent.

It may be understood that the above anisotropic conductive sheet 10 or20 comprises the non-conductive first penetrating region 11 or 21 beingreplaced with the insulating part of the conventional anisotropicconductive sheet-type elastomer connector, and theelectrically-conductive second penetrating region 12 or 22 beingreplaced with the conductive part of the anisotropic conductivesheet-type elastomer connector.

However, though it is a main object of the anisotropic conductivesheet-type elastomer connector to simply connect electrically betweenelectronic components, it is an object of the anisotropic conductivesheets 10 and 20 according to the present invention to connect betweenelectronic components as the second penetrating regions 12 and 22 whichare the signal transmitting parts is surrounded by the first penetratingregions 11 and 21 which are the insulating parts, and the firstpenetrating regions 11 and 21 are surrounded by theelectrically-conductive sheet-shaped elastomer 1 a and 1 b which is theconducting part for grounding.

For example, if a printed board and a printed board are connected by arectangular anisotropic conductive sheet 10, it is advantageous that theelectro-magnetic wave shielding property is ensured in the Junction partbetween the printed boards and the generation of noise between theprinted boards can be prevented.

Also, the non-conductive first penetrating regions 11 and 21 of theanisotropic conductive sheets 10 and 20 according to the presentinvention are replaced with a high-dielectric third penetrating region,as the second penetrating regions 12 and 22 are made signal transmittingparts and the third penetrating region, being formed to surround thesecond penetrating regions 12 and 22, is made a dielectric material,then the third penetrating region is further surrounded by theelectrically-conductive sheet-shaped elastomer 1 a and 1 b, and thesheet-shaped elastomer 1 a and 1 b is made conducting parts forgrounding.

If, for example, one coaxial cable and another coaxial cable areconnected with a circular anisotropic conductive sheet in thisconfiguration, the electro-magnetic wave shielding property is ensuredin the Junction part of the coaxial cables such that the generation ofnoise from disconnection of the coaxial cables can be prevented so as toobtain high-admittance.

Next, the anisotropic conductive sheet forming a plurality of secondpenetrating regions is described using FIGS. 2A and 2B.

In the anisotropic conductive sheet 30 shown in FIG. 2A, a plurality ofnon-conductive rectangular first penetrating regions 11 are formedvertically and horizontally as being surrounded byelectrically-conductive rectangular sheet-shaped elastomer 1 c. Then,electrically-conductive second penetrating regions 12 are formed in arectangular manner in a state of being surrounded by the firstpenetrating regions 11. The second penetrating region 12 is formed atone location for each first penetrating region 11, and the rectangularfirst penetrating region and the rectangular second penetrating region12 are positioned with the same center of gravity. A rectangularhigh-dielectric third penetrating region being composed ofhigh-dielectric material can be formed in place of the rectangular firstpenetrating region 11. The rectangular third penetrating region has thesame shape as the first penetrating region 11 and is not illustrated.

In the anisotropic conductive sheet 40 shown in FIG. 2B, a plurality ofnon-conductive circular first penetrating regions 21 are formedvertically and horizontally as being surrounded byelectrically-conductive rectangular sheet-shaped elastomer 1 d. Then,electrically-conductive second penetrating regions 22 are formed in acircular shape in a state of being surrounded by the respective circularfirst penetrating regions 21. The second penetrating region 22 is formedone location for each first penetrating region 21, and the circularfirst penetrating region and the circular second penetrating region 22are positioned in a concentric manner. The circular first penetratingregion 21 can be replaced with a circular third penetrating regioncomposed of high-dielectric material. Because the third penetratingregion has the same shape as the first penetrating region, theanisotropic conductive sheet having the third penetrating region is notillustrated.

Although the second penetrating regions 12 and 22 are aligned withregularity in a matrix in the foregoing anisotropic conductive sheets 30and 40, the second penetrating regions 12 and 22 can be placed scatteredrandomly as desired. In addition, the second penetrating regions 12 and22 can be aligned, evenly spaced, in one row.

When using the anisotropic conductive sheet 30 shown in FIG. 2A to joinfine pitch electronic components, the length D1 of the non-conductivefirst penetration region 11 (or third penetration region) is preferably100 μm or shorter and the length D2 of the second penetrating region 12is preferably 50 μm or shorter. In addition, the distance D3 betweenadjacent first penetrating regions 11 (or third penetrating regions) ispreferably 30 μm or shorter. In such range, the alignment pitch distancePX between adjacent second penetrating regions 12 can be 130 μm orlonger.

In the embodiment in FIG. 2A, width W1 of the non-conductive firstpenetrating region 11 (or third penetrating region) is approximately 80μm, the alignment pitch distance PY to the adjacent first penetratingregion 11 is approximately 130 μm, and the width W2 of the secondpenetrating region 12 is approximately 50 μm. However, it should beunderstood that width W1, W2 and distance PY can be longer (or larger)than this in other embodiments.

In the embodiment in FIG. 2B, if the alignment pitch PX and PY of thesecond penetrating region 22 is adjusted to the land pattern placementof a printed board, the second penetrating region 22 can be consideredto be aligned in 1/10 inch- or, in other words, with 2.54 mm-intervals.It should be understood that the alignment pitch PX and PY of the secondpenetrating region 22 can be longer (or larger) or shorter (or smaller)than this in other embodiments.

Next, the manufacturing method of the anisotropic conductive sheet 30 inFIG. 2A is described in reference to FIGS. 3, 4A and 48.

First, a plurality of quadrangular prism cores 31 are providedvertically and horizontally in a box-shaped cuboid frame (notillustrated). Then, compounded rubber prepared by kneading crudecaoutchouc with electrically-conductive fine particles such as graphiteand small amount of sulfur and additives is placed in this frame andmolded. Furthermore, the compounded rubber is vulcanized by heating, andthe conductive block 1 e as shown in FIG. 3 is obtained.

Next, as shown in FIG. 4A, a core 31 is removed from the conductiveblock 1 e and second quadrangular prism core 33 is provided to standwithin a rectangular penetration hole 32. Then, unvulcanizednon-conductive rubber (or rubber having been kneaded with fine particlesof ferroelectric substance such as barium titanate) is poured into thepenetration hole 32, and unvulcanized non-conductive block 12 a (ordielectric block) is formed. Then, the unvulcanized non-conductive block12 a (or dielectric block) and the vulcanized conductive block 1 e arebonded by heating.

Next, the second core 33 is removed from the conductive block 1 e andunvulcanized conductive rubber 11 a having been kneaded with conductivematerial such as silver is poured into the second penetration hole fromwhich the second core 33 had been removed. Then, the unvulcanizedconductive rubber 11 a and the vulcanized non-conductive block 12 a (ordielectric block) are bonded by heating.

By cutting along an X-X cutting-plane line the anisotropic conductiveblock 50 shown in FIG. 4B, which is manufactured as described above,with the anisotropic conductive sheet 30 shown in FIG. 2A is obtained.

The anisotropic conductive block 50 can be cut with a blade, such ashard metal cutter, ceramic cutter and the like, by a grinding stone suchas fine cutter, by a saw such as a saw, and by other cutting instrumentsand cutting devices (may include a non-contact cutting device such as alaser cutting machine).

Cutting fluid such as cutting oil can also be used in order to preventoverheating when cutting in order to obtain a clean cut surface, and forother purposes, and it also can be cut in a dry condition.

In this way, it is rather easy to make an anisotropic conductive sheetcomprising thin sheet-shaped elastomer as a main body and an anisotropicconductive sheet comprising thick sheet-shaped elastomer as a main body,which used to be believed difficult. Although the thickness ofsheet-shaped elastomer is generally about 1 mm, it can be about 100 μmor thinner (about 50 μm or thinner if particularly desired) when makingit thinner and on the other hand it also can be several millimeters. Thethickness of this example is about 1 mm.

Next, the manufacturing method of the anisotropic conductive sheet inFIG. 2B is described in reference to FIGS. 5, 6A and 6B.

First, a plurality of cylindrical cores 41 are provided to standvertically and horizontally in a box-shaped cuboid frame (notillustrated). Then, compounded rubber comprising crude rubber havingbeen kneaded with electrically-conductive fine particles such asgraphite and small amount of sulfur and additive is placed in this frameand molded. Furthermore, it is vulcanized by heating, and the conductiveblock 1 f shown in FIG. 5 is obtained.

Next, as shown in FIG. 6A, cylindrical core 41 is removed from theconductive block 1 f and second cylindrical core 43 is stuck within acircular penetration hole 42. Then, unvulcanized non-conductive rubber(or rubber having been kneaded with fine particles of ferroelectricsubstance such as barium titanate) is poured into the circularpenetration hole 42, and unvulcanized non-conductive block 22 a (ordielectric block) is formed. Then, the unvulcanized non-conductive block22 a (or dielectric block) and the vulcanized conductive block 1 f arebonded by heating.

Next, the second cylindrical core 43 is removed from the conductiveblock 1 f and unvulcanized conductive rubber 21 a having been kneadedwith conductive material such as silver is poured into the secondcircular penetration hole after removing the cylindrical second core 43.Then, the unvulcanized conductive rubber 21 a and the vulcanizednon-conductive block 22 a (or dielectric block) are bonded by heating.

By cutting along an X-X cutting-plane line the anisotropic conductiveblock 60 shown in FIG. 6B which is manufactured as described above, theanisotropic conductive sheet 40 shown in FIG. 2B is obtained.

Next, other manufacturing methods for obtaining an anisotropicconductive sheet similar to the anisotropic conductive sheet 30 shown inFIG. 2A are described. FIG. 7 shows an anisotropic conductive sheet 70which uses metallic metal layer as the second penetrating region.

Although the anisotropic conductive sheet 70 of the present embodimentis a rectangular sheet, it can also be applied to sheet-shapedcomponents in a shape other than the rectangular. In the anisotropicconductive sheet 70, metallic metal layer 71 is sandwiched by a concavecomponent 73 and a non-conductive strip-shaped component 72 beingcomposed of non-conductive sub-components, which surround the metallayer 71. Furthermore, the non-conductive strip-shaped component 72 andthe concave component 73 are configured so as to be sandwiched andsurrounded by electrically-conductive strip-shaped components 74, 75,and 76, being composed of electrically-conductive components.

In this embodiment, the non-conductive strip-shaped component 72 and theconcave component 73 form the rectangular first penetrating region, andthe metal layer 71 forms the rectangular second penetrating region.

When forming the high-dielectric third penetrating region in place ofthe non-conductive first penetrating region in the anisotropicconductive sheet 70, non-conductive strip-shaped component 72 can bereplaced with strip-shaped component formed from dielectric material.Similarly, non-conductive concave component 73 can be replaced withstrip-shaped component formed from dielectric material.

The metallic metal layer 71, and the non-conductive strip-shapedcomponent 72 and concave component 73 can be coupled, and in turn thecomponents 72, 73 and conductive strip-shaped components 74 to 78 can becoupled by a coupling agent. For the anisotropic conductive sheet 70 ofthis embodiment, Mitsubishi Plastics, Inc. product silicone rubber,Shin-Etsu Polymer Co., Ltd. product silicone rubber and the like areemployed as non-conductive elastomer, and Shin-Etsu Polymer Co., Ltd.product silane coupling agent is used as the coupling agent. Themetallic metal layer 71 can include a metal layer of one type of metaland the metal layer 71 can comprise multi-layered conductivethin-layers.

FIG. 8 is a partially enlarged view enlarging the upper left corner ofFIG. 7 and shows the non-conductive strip-shaped component 72 andconcave component 73 in more detail. As shown in FIG. 8, non-conductivestrip-shaped component 72 and concave component 73 are mutually coupledwith the coupling agent via an adhesive layer 91.

When the metal layer 71, non-conductive strip-shaped component 72 andconcave component 73 are not accurately aligned, space 92 is generatedon both sides of metal layer 71. However, if the metal layer 71 issufficiently thin, such spaces may not exist. These spaces can be leftopen simply as space or can be filled with coupling agent or otherfiller. Generally, if the spaces are left open, crack tip part of asharp angle can easily progress as cracks and, as a result, the couplednon-conductive strip-shaped component 72 and concave component 73 maybecome separated. Therefore, it is preferable, from this perspective, tofill the spaces with filler.

In FIG. 8, the length of the second penetrating region formed in themetal layer 71 is D2 and the width is W2. The length and width of thefirst penetrating region formed in the non-conductive strip-shapedcomponent 72 and concave component 73 are D1 and W1, respectively.Further, the width of conductive strip-shaped component 74 is t₁₁, thewidth of conductive strip-shaped component 75 is t₁₂, and the width ofconductive strip-shaped component 76 is t₂₁ or t₂₂.

Although each of these measurements can be set arbitrarily, in thepresent embodiment, t₁₁=t₁₂ and t₂₁=t₂₂. Further, though the length D2and width W2 of the second penetrating region formed in the metal layer71 can also be set arbitrarily, length D2 can be set, for example, toabout 50 μm.

Although the thickness, width and length of the anisotropic conductivesheet of the present embodiment is not limited, when using theanisotropic conductive sheet to connect between a circuit board and theterminal of an electronic component, it is preferable that it is of asize consistent with these measurements. In these cases, width andlength are generally 0.5 to 3.0 cm×0.5 to 3.0 cm and thickness is 0.5 to2.0 mm.

The thickness of these strip-shaped components is the same in thisexample, and therefore, the thickness of the sheet is the thicknessshown by T in FIG. 8. As stated earlier, the adjacent non-conductivestrip-shaped component 72 and concave component 73 are coupled by thecoupling agent and then they constitute one sheet as shown in FIG. 7.Here, the coupling agent for coupling is non-conductive, and thenon-conductivity in the surface direction of the sheet is ensured.

Next, a method for manufacturing the anisotropic conductive sheet 70 ofthe foregoing embodiment is described in reference to FIGS. 9 to 13.FIG. 9 shows a metallic metal rod 71 a and a board with metal 712 formedfrom non-conductive board-shaped component 72 a. The metal rod 71 abecomes metal layer 71 in FIG. 7 and non-conductive board-shapedcomponent 72 a becomes a non-conductive strip-shaped component 72 inFIG. 7.

Though metal rods 71 a in FIG. 9 can be prepared by a variety ofmethods, they are deposited in the form by sputtering in thisembodiment. In other words, the non-conductive board-shaped component 72a is a substrate, target matching the components of the metal rod 71 ato be formed is adjusted and metal rod 71 a is attached by sputteringdevice. The width of each metal rod 71 a and intervals thereof can beadjusted by performing appropriate masking. The non-conductiveboard-shaped component 72 a of this embodiment is non-conductiveelastomer, and therefore modifications should be made such that thesubstrate temperature does not rise excessively, for example, usingmagnetron sputtering, ion beam sputtering and the like.

FIG. 10 shows an aspect wherein a laminated body 100 is formed bylayering a non-conductive bridge-shaped component 73 a, which is theconcave component 73 in FIG. 7, onto a board with metal 712. Laminatedbody 100 is formed by applying coupling agent between the board withmetal 712 and non-conductive bridge-shaped component 73 a and couplingboth components.

FIG. 11 shows an aspect wherein the laminated body 100 and conductiveboard 74 a and 75 a formed from electrically-conductive material arefurther layered. Conductive board 74 a becomes theelectrically-conductive strip-shaped component 74 of FIG. 7, andconductive board 75 a becomes the electrically-conductive strip-shapedcomponent 75 of FIG. 7. A plurality of laminated bodies 100 andconductive board 75 a are layered such that metal rod 71 a is aligned inparallel. The widths of laminated body 100 and conductive board 74 a and75 a are the same, coupling agent is applied between the laminated body100 and conductive board 74 a and 75 a, the laminated body 100 andconductive board 74 a and 75 a are coupled by coupling agent, and thelaminated body 102 shown in FIG. 12 is formed.

The laminated body 102 which has been formed by the foregoing process iscut such that the width of the first penetrating region (namely, theregion formed by non-conductive strip-shaped component 72 and concavecomponent 73) of the anisotropic conductive sheet shown in FIG. 13 maybe desirable width W1. Then, a plurality of laminated bodies 102 whichhave been cut evenly to become width W1 is aligned as shown in FIG. 12.

FIG. 13 shows an aspect wherein laminated body 103 is formed by furthersandwiching conductive sheet component 78 a between a plurality oflaminated bodies 102. The depth and height of conductive sheet component76 a is the same as the depth and height in the cut surface of laminatedbody 102, respectively, and conductive sheet components 76 a are stackedsuch that directions of metal rods 71 a are all uniform (such as to beparallel). The conductive sheet component 76 a becomes theelectrically-conductive strip-shaped component 78 in FIG. 7. Thecoupling agent is applied between these laminated bodies 102 andconductive sheet components 78 a, laminated bodies 102 and conductivesheet components 76 a are coupled with coupling agent, and block 103 isformed.

FIG. 13 shows the process for cutting block 103 which has been formed bythe foregoing process. The block 103 is cut along the X-X line with anarbitrary thickness T, and an anisotropic conductive sheet 70 ofthickness T is obtained. This thickness T is equivalent to T in FIG. 7,t in FIGS. 1A, 1B, 2A and 2B. Therefore, the conventionally difficultformation of thin anisotropic conductive sheets and the formation ofthick anisotropic conductive sheets can be facilitated. Although thethickness is generally about 1 mm, it can be about 100 μm or thinner(about 50 μm or thinner if particularly desired) when making it thin andit can also be several millimeters. It is about 1 mm in this example.

The metallic metal layer 71 is, for example, copper (Cu). The copper canbe plated with electrically-conductive coating beforehand, or thecoating can be applied after anisotropic conductive sheet is completed.In addition, if the high-dielectric third penetrating region is formedin place of the non-conductive first penetrating region in anisotropicconductive sheet 70, strip-shaped component formed from dielectricmaterial is formed in place of non-conductive strip-shaped component 72and concave component formed from dielectric material can be formed inplace of non-conductive concave component 73, respectively, by usingdielectric sheet formed from dielectric material in place of thenon-conductive board-shaped component 72 a comprising board with metal712 and dielectric bridge-shaped component formed from dielectricmaterial in place of non-conductive bridge-shaped component 73 a. Inthis case, strip-shaped component formed from dielectric component andconcave component formed from dielectric component form the thirdpenetrating region.

Because, in this way, the anisotropic conductive sheet surrounds theelectrically-conductive second penetrating region with thenon-conductive penetrating region and further surrounds thenon-conductive first penetrating region with the conductive elastomer,while ensuring insulation and elasticity in the surface direction aselastomer connector, this is effective in that electrostatic shield isprovided between the electronic components connected to this anisotropicconductive sheet. For example, it can be prevented that the shield isbroken by providing this anisotropic conductive sheet to connectioncomponents between the coaxial cable and the circuit board.

Further, the areas and pitches of the non-conductive first penetratingregion (or high-dielectric third penetrating region) and theelectrically conductive second penetrating region can be set freely, anddesired fine pitch can be easily attained by high-integration. Further,because the first penetrating region, second penetrating region andsheet-shaped elastomers are joined (rubber bridge) chemically, it iseffective in reducing the threat of deficiency due to missing conductiveparts and the like, which may occur when using linear metals asconductive parts.

In the anisotropic conductive sheet, because the electrically-conductivesecond penetrating region is surrounded by high-dielectric thirdpenetrating region and the high-dielectric third penetrating region isfurther surrounded by conductive elastomer, low inductance between theconnection of electronic components is possible by making the thicknessof this anisotropic sheet about 0.5 mm to 2 mm. Furthermore,high-admittance due to ferroelectric substance can also be expected.

1. An anisotropic conductive sheet being electrically conductive in onlyone direction; comprising: electrically-conductive sheet-shapedelastomer; at least one non-conductive first penetrating region beingformed as being surrounded by the sheet-shaped elastomer; and anelectrically-conductive second penetrating region being formed as beingsurrounded by the at least one non-conductive first penetrating region.2. The anisotropic conductive sheet according to claim 1, wherein thesecond penetrating region is interspersed in the sheet-shaped elastomer.3. The anisotropic conductive sheet according to claim 1, wherein thesecond penetrating region is aligned with regularity in the sheet-shapedelastomer.
 4. The anisotropic conductive sheet according to claim 1,wherein the second penetrating region has higher conductivity than thesheet-shaped elastomer.
 5. The anisotropic conductive sheet according toclaim 1, wherein the first penetrating region and the second penetratingregion are formed in a concentric manner.
 6. The anisotropic conductivesheet according to claim 1, wherein the first penetrating region and thesecond penetrating region are formed in a rectangular manner, and therectangular first penetrating region and the rectangular secondpenetrating region are positioned with a same center of gravity.
 7. Ananisotropic conductive sheet being electrically conductive in only onedirection, wherein: the anisotropic conductive sheet has anelectrically-conductive sheet-shaped elastomer; at least onehigh-dielectric third penetrating region is formed as being surroundedby the sheet-shaped elastomer; and an electrically-conductive secondpenetrating region is formed as being surrounded by the thirdpenetrating region.
 8. The anisotropic conductive sheet according toclaim 7, wherein the second penetrating region is interspersed in thesheet-shaped elastomer.
 9. The anisotropic conductive sheet according toclaim 7, wherein the second penetrating region is aligned withregularity in the sheet-shaped elastomer.
 10. The anisotropic conductivesheet according to claim 7, wherein the second penetrating region hashigher conductivity than the sheet-shaped elastomer.
 11. The anisotropicconductive sheet according to claim 7, wherein the third penetratingregion and the second penetrating region are formed in a concentricmanner.
 12. The anisotropic conductive sheet according to claim 7,wherein the third penetrating region and the second penetrating regionare formed in rectangular, and the rectangular third penetrating regionand the rectangular second penetrating region are placed with a samecenter of gravity.
 13. The anisotropic conductive sheet according toclaim 7, wherein the third penetrating region comprises ferro electricsubstance.
 14. A pair of electronic components which are connected withthe anisotropic conductive sheet according to claim
 1. 15. A pair ofelectronic components which are connected with the anisotropicconductive sheet according to claim 7.